/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.propertyeditors;

import java.beans.PropertyEditorSupport;

import org.springframework.lang.Nullable;
import org.springframework.util.StringUtils;

/**
 * Editor for a {@link Character}, to populate a property
 * of type {@code Character} or {@code char} from a String value.
 *
 * <p>Note that the JDK does not contain a default
 * {@link java.beans.PropertyEditor property editor} for {@code char}!
 * {@link org.springframework.beans.BeanWrapperImpl} will register this
 * editor by default.
 *
 * <p>Also supports conversion from a Unicode character sequence; e.g.
 * {@code u0041} ('A').
 *
 * @author Juergen Hoeller
 * @author Rob Harrop
 * @author Rick Evans
 * @see Character
 * @see org.springframework.beans.BeanWrapperImpl
 * @since 1.2
 */
public class CharacterEditor extends PropertyEditorSupport {

    /**
     * The prefix that identifies a string as being a Unicode character sequence.
     */
    private static final String UNICODE_PREFIX = "\\u";

    /**
     * The length of a Unicode character sequence.
     */
    private static final int UNICODE_LENGTH = 6;


    private final boolean allowEmpty;


    /**
     * Create a new CharacterEditor instance.
     * <p>The "allowEmpty" parameter controls whether an empty String is to be
     * allowed in parsing, i.e. be interpreted as the {@code null} value when
     * {@link #setAsText(String) text is being converted}. If {@code false},
     * an {@link IllegalArgumentException} will be thrown at that time.
     *
     * @param allowEmpty if empty strings are to be allowed
     */
    public CharacterEditor(boolean allowEmpty) {
        this.allowEmpty = allowEmpty;
    }

    @Override
    public String getAsText() {
        Object value = getValue();
        return (value != null ? value.toString() : "");
    }

    @Override
    public void setAsText(@Nullable String text) throws IllegalArgumentException {
        if (this.allowEmpty && !StringUtils.hasLength(text)) {
            // Treat empty String as null value.
            setValue(null);
        } else if (text == null) {
            throw new IllegalArgumentException("null String cannot be converted to char type");
        } else if (isUnicodeCharacterSequence(text)) {
            setAsUnicode(text);
        } else if (text.length() == 1) {
            setValue(Character.valueOf(text.charAt(0)));
        } else {
            throw new IllegalArgumentException("String [" + text + "] with length " +
                    text.length() + " cannot be converted to char type: neither Unicode nor single character");
        }
    }

    private boolean isUnicodeCharacterSequence(String sequence) {
        return (sequence.startsWith(UNICODE_PREFIX) && sequence.length() == UNICODE_LENGTH);
    }

    private void setAsUnicode(String text) {
        int code = Integer.parseInt(text.substring(UNICODE_PREFIX.length()), 16);
        setValue(Character.valueOf((char) code));
    }

}
